Method and apparatus for pH recording

Abstract

For continuous or intermittent monitoring or recording of the in vivo plasma pH of a patient, the patient's acid base status is established with performance of at least one in vitro determination on a blood sample from the patient, and for a period of some hours thereafter, the patient's in vivo plasma pH is determined on the basis of this initial acid base status and the results of non-invasive measurements of the patient's actual blood Pco 2 .

I claim: 
     
       1. A method for continous or intermittent monitoring of a patient's in vivo plasma pH value, comprising establishing the patient's acid base status with performance of at least one in vitro determination on a blood sample withdrawn from the patient, and thereafter determining the patient's in vivo plasma pH on the basis of the thus established initial acid base status and on the basis of continuously or intermittently registered results of a non-invasive measurement of the patient's actual blood Pco 2 . 
     
     
       2. A method according to claim 1, comprising establishing the patient's initial acid base status with performance of an in vitro determination of pH and Pco 2  on an arterial or capillary blood sample withdrawn from the patient and transferred anaerobically. 
     
     
       3. A method according to claim 1, comprising establishing the patient's initial acid base status with performance of in vitro determination of pH on an arterial or capillary blood sample withdrawn from the patient and transferred anaerobically and on the basis of the result of a non-invasive measurement of the patient's blood Pco 2  performmed simultaneously with the withdrawal of the blood sample. 
     
     
       4. A method according to claim 2, comprising calibrating the in vivo Pco 2  measuring equipment on the basis of the result of the in vitro Pco 2  measurement and on the basis of the result of a non-invasive measurement of the patient's blood Pco 2  performed simultaneously with the withdrawal of the arterial blood sample. 
     
     
       5. A method according to claim 2, comprising additionally performing, on the anaerobically transferred arterial or capillary blood sample, a determination of the oxygen saturation, or registering the result of a non-invasive oxygen saturation determination performed simultaneously with the blood sample withdrawal, and including, in the determinations of the patient's in vivo plasma pH for a period thereafter, the result of non-invasive oxygen saturation determinations performed at the actual times. 
     
     
       6. A method according to claim 1, comprising establishing the patient's initial acid base status with performance of in vitro determination of pH, Pco 2  and an additional blood parameter, said additional blood parameter being selected from the group consisting of the hemoglobin content and another blood parameter which is a function of the hemoglobin content, on a non-anaerobically transferred blood sample withdrawn from the patient, and on the basis of the result of non-invasive measurement of the patient's blood Pco 2  performed simultaneously with the withdrawal of the blood sample. 
     
     
       7. A method according to claim 6, comprising additionally performing, on the blood sample, an oxygen saturation determination and registering the result of a non-invasive oxygen saturation determination performed simultaneously with the withdrawal of the blood sample, any differences between the oxygen saturation determination and the result of the non-invasive oxygen saturation determination being used to correct the initial acid base status; and in the determinations of the patient's in vivo plasma pH performed for a period thereafter, including the results of non-invasive oxygen saturation determinations performed at the actual times. 
     
     
       8. An apparatus for continuous or intermittent monitoring of a patient's in vivo plasma pH, comprising a first input means (13a; 20a) for signals representing results of a non-invasive Pco 2  measurement and a second input means (25a; 27a) for introduction of at least one blood parameter determined by in vitro measurement, a pH registration unit (12; 12a), a conversion means 21, said pH registration unit being connected to the first input means (13a; 20a) through the conversion means (21), the conversion means (21) being adapted to perform the conversion of the received Pco 2  signals to pH units as a function of a parameter set read into the conversion means (21), and representing an initial acid base status, the said parameter set comprising at least one blood parameter determined by in vitro measurement introduced via the second input means (25a; 27a). 
     
     
       9. An apparatus according to claim 8, comprising a means (24; 26) for introducing at least one blood parameter determined in vitro, said means for introducing at least one blood parameter determined in vitro (24; 26) being connected to the second input means (25a; 27a). 
     
     
       10. An apparatus according to claim 9, in which the means (24; 26) for introduction of at least one blood parameter determined in vitro is a keyboard. 
     
     
       11. An apparatus according to claim 9, in which the means (24; 26) for the introduction of at least one blood parameter determined in vitro is pH measuring equipment. 
     
     
       12. An apparatus according to claim 9, in which the means (24; 26) for introduction of at least one blood parameter determined in vitro is blood gas equipment. 
     
     
       13. An apparatus according to claim 8, which in addition to the pH registration unit (12; 12a) comprises a Pco 2  registration unit (15) connected to the first input means (13a; 20a) for signals representing the result of a non-invasive Pco 2  measurement. 
     
     
       14. An apparatus according to claim 8, comprising a third input means (14a) for signals representing the result of a non-invasive Po 2  measurement or a non-invasive oxygen saturation measurement, said signals representing the result of a non-invasive Po 2  measurement or a non-invasive oxygen saturation measurement being at least a part of the parameter set, the said third input means communicating with the conversion means (21). 
     
     
       15. An apparatus according to claim 12, and comprising Po 2  registration unit (16) communicating with the said third input means (14a). 
     
     
       16. An apparatus according to claim 1, comprising a synchronization means (28; 29), at the activation of which the non-invasively measured Pco 2  value registered at the activation time and optionally the non-invasively measured Po 2  value registered at the activation time is/are stored in the conversion means (21).